1. Field of the Invention
This invention generally relates to medical devices and, more specifically, to medical tubing adapted for insertion into a body tissue or cavity having variable characteristics and method of making same.
2. Discussion of Related Art
Medical tubing includes tubing used as catheters, drain tubes, access ports, endoscope bodies and the like. The requirements for each type of medical tubing will depend on its use. In particular, a specific length of medical tubing may vary depending on each application. For example, a specific length of medical tubing may need to be very flexible and yet pushable, or it may need to be thin-walled and yet kink-resistant. In addition, the tubing may need to exhibit these properties in only specific regions.
Most medical tubing is extruded from a single plastic material in a continuous forming process. Certain characteristics or variations may be imparted to the extruded tubing by altering the speed or the tension of the extruded material as it exits and cools from the extrusion machine. However, the variations are limited by the fact that a single material is extruded. Recent advances in extrusion technology have allowed the co-extrusion of multiple materials. This provides some usable variations in extruded tubing. Nevertheless, this is still a linear process and is still limited by the continuous flow of the extruded materials.
Accordingly, there is a need for a medical tubing having a length with variable characteristics and a method of making the tubing such that variations can occur along the length of the manufactured tubing. For instance, a length of the tubing may be rigid for a length, becomes flexible for a length and then becomes rigid again for another length. It is also desirable to have large variations in the diameter of the tubing. In another application, there may be a need for a tube that is extremely kink-resistant in a specific region. Kink-resistance with very thin walls is not obtainable through the current extrusion processes.